Fix #121134: Hide Proportional Editing for armature editmode

When transforming, both `TransConvertType_EditArmature` /
`TransConvertType_Pose` get disabled from proportional editing
(`TransInfo` gets flagged `CTX_NO_PET` in `init_proportional_edit`).
This is intentional.

UI checks the mode and showing proportional editing properties was
already skipped for 'POSE' mode, but armatures in 'EDIT' mode would
still show them.

To resolve, also skip the UI for `EDIT_ARMATURE` mode.

Pull Request: https://projects.blender.org/blender/blender/pulls/121205

scripts/startup/bl_ui/space_view3d.py

@@ -787,7 +787,12 @@ class VIEW3D_HT_header(Header):
             )
 
         # Proportional editing
-        if object_mode in {'EDIT', 'PARTICLE_EDIT', 'SCULPT_GPENCIL', 'EDIT_GPENCIL', 'OBJECT'}:
+        if object_mode in {
+            'EDIT',
+            'PARTICLE_EDIT',
+            'SCULPT_GPENCIL',
+            'EDIT_GPENCIL',
+                'OBJECT'} and context.mode != 'EDIT_ARMATURE':
             row = layout.row(align=True)
             kw = {}
             if object_mode == 'OBJECT':